1. Field of the Invention
The invention relates to a door latch having an adjustable backset distance. More specifically, the invention relates to such a door latch in which the backset distance can be set to one of two predetermined distances.
2. Description of Prior Art
Door latches having adjustable backset distances are known in the art as illustrated in, for example, U.S. Pat. Nos. 4,593,542, Rotondi et al., June 10, 1986, 4,602,490, Glass et al, July 29, 1986, 4,623,174, Trull et al., Nov. 18, 1986 and 4,639,025, Fann et al., Jan. 27, 1987.
In the '025 patent, to change the backset distance, it is necessary to move both extension member 20, crank plate holding means 32 and crank plate 31, relative to pivot pin 26 which then occupies one of two positions 132 of aperture 131 of extendable member 123 of bolt extension member 20.
In the '490 patent, to change the backset distance, a floating pin 45 is pushed downwardly, against the force of a spring 51, in legs 62 of slot 60 of casing 20, and legs 68 or 69 of slot 65 of driver bar 30. Driver bar 30, slide 35 (for spindle 16 and dog 27) are moved from one backset distance to another. In order to adjust the backset distance in accordance with the teachings in this patent, screws 18 must be removed from slide 35 and holes 75 and 76 in casing 20 before the adjustment can be effected.
In the '542 patent, the latch cam 56 is coupled to at least one side plate 40 (in the illustrated embodiments to side plates 40 and 41) and the side plates and latch cam are slidable within latch case 22 to adjust the distance of the backset.
The '849 patent, which is a division of the '542 patent, teaches the same arrangement.
Finally, in the '174 patent, the backset distance is adjusted by selecting one of two inserts, 40 or 40', which are different lengths.